1. Field of the Invention
This invention relates to an apparatus for making a nonwoven web comprising a toothed opening roller for opening a lap, which roller is adapted to be driven at such a surface speed that the fibers of the opened lap are thrown off under centrifugal force, a revolving air-permeable collecting surface member which has an at least substantially flat fiber-receiving portion, and a suction box, which adjoins said fiber-receiving portion of the collecting surface member on the side which is remote from the opening roller.
2. Description of the Prior Art
In apparatuses of that kind the toothed opening roller is used to disintegrate the lap into individual fibers, which are detached from the opening roller, preferably with the assistance of a blown air stream that is directed tangentially to the opening roller, and in a freely flowing state are deposited on a collecting surface member, which extends transversely to the stream of fibers and which is subjected to suction. The fibers are deposited in a random orientation in a plane which is parallel to the collecting surface member. But a deposition of fibers over the thickness of the nonwoven web will assist the formation of thicker nonwoven webs and for this reason said known apparatuses are less suitable for the making of bulky random-laid nonwoven webs having a low density.
If the stream of fibers which fly from the opening roller is not directed to a sieve belt which extends transversely to the stream of fibers, but is caught in the generally triangular space between two sieve drums, which revolve in mutually opposite senses and are subjected to suction in the generally triangular space, and the nonwoven web forming on the sieve drums is conveyed away between said drums, it will be possible to ensure symmetrical relations as regards the surface structure of the nonwoven web but the conditions which affect the density of the nonwoven web will be similar to those obtained if a sieve belt is used as a collecting surface member.